The controls are like that on purpose.
I was trying to emulate playing on older consoles, back when you would have to look up and down by pressing buttons on a controller. Such as R1 and L1 on a PS1. Back when analog sticks didn't exist yet or weren't used prominently.
I just didn't include input mappings for a controller which in hind sight was a bit of a dumb-dumb decision. But personally I think the game plays better on the keyboard anyway.